Blood bags have to bear all the particulars, whether coded or in plain language, that are needed to identify the donor and to give information on the characteristics of the blood after it has been analysed. Hitherto, the bags have been marked manually by sticking on suitable labels in accordance with the results of the analyses. These operations, which are long and tedious on account of the checks that have to be carried out, and which do not preclude all risk of error, have led to the development and production of an automatic labelling machine which makes such operations faster and more reliable thanks to the fact that it incorporates checking devices.